1. Field of the Invention
This invention relates to an ultrasonic diagnostic system or an ultrasound imaging system using a nonlinearity of an examined body with respect to propagation of ultrasonic wave.
2. Description of the Related Art
In general, a human body has a nonlinearity with respect to propagation of ultrasonic wave. Therefore, as the ultrasonic wave is propagated in the human body, it is distorted by the nonlinearity. An effective nonlinearity of a human body tends to depend on the amplitude of ultrasonic wave propagated therein.
There is a known ultrasonic diagnostic system using such a nonlinearity of a body to be examined. The known ultrasonic diagnostic system includes a transducer to which an electric drive pulse signal is fed during a transmission process. The transducer converts the electric drive pulse signal to a corresponding ultrasonic pulse wave emitted into the examined body. The amplitude of the electric drive pulse signal is changed between two levels to vary the amplitude of the ultrasonic pulse wave. Thus, the known ultrasonic diagnostic system requires a power feed device designed to change the amplitude of the electric drive pulse signal. Such a power feed device causes a complicated structure of the known ultrasonic diagnostic system.